Modeling Receiver Functions in the Mississippi Embayment: Effect of a Thick Sedimentary Cover

Receiver functions studies are usually conducted under the assumption of first order sensitivity to S-wave velocity structure and second order sensitivity to P-wave velocity or density. In thepresence of a significant sedimentary cover, most of the signal that is observed in the receiver function consists of energy trapped within the sedimentary layer as multiply reverberated phases containing several P and S segments, not basically Ps conversions. One consequence is an increased sensitivity to P-wave structure and, as a result, to Poisson's ratio and density. Another common assumption in receiver function studies is that attenuation has a second order effect on the waveforms. When the existence of a sedimentary cover is taken into account, we do observe -~as expected~- a stronger signature of attenuation structure in multiply reverberated phases but still it seldom modifies the synthetic waveform within the frequency range of interest. In this study we present some numerical experiments to get an insight to the sensitivity of receiver functions. Our goal is to map what can be learned from receiver function studies in sedimentary environments. To illustrate our work, we also provide the results of modeling receiver functions computed using signals recorded on several stations located in the Mississippi Embayment, where the significant number of independent geophysical studies carried out establish an excellent setting for comparison.